f humanity ever wants to colonize a planet beyond the solar system, it's going to need a really big spaceship. The founding population of an interstellar colony should consist of 20,000 to 40,000 people, said Cameron Smith, an anthropologist at Portland State University in Oregon. Such a large group would possess a great deal of genetic and demographic diversity, giving the settlement the best chance of survival during the long space voyage and beyond, he explained.

The robots, known as Spheres (Synchronised Position Hold, Engage, Reorient, Experimental satellites), currently have limited capabilities.

It is hoped the smartphones, powered by Google's Project Tango, will equip the robots with more functionality.

The robots have been described by experts as "incredibly clever".

When Nasa's robots first arrived at the International Space Station in 2006, they were only capable of precise movements using small jets of CO2, which propelled the devices forwards at around an inch per second.

"We wanted to add communication, a camera, increase the processing capability, accelerometers and other sensors," Spheres project manager Chris Provencher told Reuters.